Razor blades are typically formed of a suitable metallic sheet material such as stainless steel, which is slit to a desired width and heat-treated to harden the metal. The hardening operation utilizes a high temperature furnace, where the metal may be exposed to temperatures greater than 110° C. for up to 10 seconds, followed by quenching.
After hardening, a cutting edge is formed on the blade. The cutting edge typically has a wedge-shaped configuration with an ultimate tip having a radius less than about 1000 angstroms, e.g., about 200-300 angstroms.
Various coatings may be applied to the cutting edge. For example, hard coatings such as diamond, amorphous diamond, diamond-like carbon (DLC) material, nitrides, carbides, oxides or ceramics are often applied to the cutting edge or the ultimate tip to improve strength, corrosion resistance and shaving ability. Interlayers of niobium or chromium containing materials can aid in improving the binding between the substrate, typically stainless steel, and the hard coatings. A polytetrafluoroethylene (PTFE) outer layer can be used to provide friction reduction.
It is important that these coatings be applied, and any other post-hardening processing steps be performed, under sufficiently low temperature conditions so that the hardened, sharpened steel is not tempered. If the steel is tempered it will lose its hardness and may not perform properly during use.
Examples of razor blade cutting edge structures and processes of manufacture are described in U.S. Pat. Nos. 5,295,305; 5,232,568; 4,933,058; 5,032,243; 5,497,550; 5,940,975; 5,669,144; EP 0591334; and PCT 92/03330, which are hereby incorporated by reference.